1. Field of the Invention
The present invention relates to a control device for a hybrid vehicle. In particular, the invention relates to a control device for a hybrid vehicle that can perform cylinder deactivation operation.
2. Description of the Related Art
In general, parallel hybrid vehicles are controlled in various ways such that the driving output of the engine of a hybrid vehicle is assisted by a motor at the time of acceleration, while at the time of deceleration, battery is charged by deceleration regeneration, so that the state of charge (electrical energy) of the battery can be maintained while satisfying the requirements of the driver. Furthermore, since the engine and the motor are connected in series from the structural point of view, the structure of the vehicle becomes simple, and the weight of the whole system may be reduced. Therefore, a high degree of freedom can be obtained in loading equipment.
In order to avoid the influence of engine friction (engine brake) at the time of deceleration regeneration, a particular structure for the aforementioned parallel hybrid vehicle has been proposed to provide a clutch between the engine and motor as shown, for example, refer to Japanese Unexamined Patent Application, First Publication No. 2000-97068.
However, when the clutch is installed between the engine and motor, a problem occurs in that the construction becomes complicated by installing the clutch and the loading of equipment becomes more difficult, and, in addition, due to usage of the clutch, the transmission efficiency of the power transmission system is reduced during deceleration regeneration and during traveling of the vehicle.
In contrast, at the time of deceleration, it has been offered to perform a cylinder deactivation operation by deactivating at least one cylinder for reducing the pumping loss of the engine. This improves the regeneration efficiency of the motor during deceleration.
However, in the control device of a hybrid vehicle which reduces the engine friction by deactivating cylinders at the time of deceleration and which increases the amount of regeneration by the amount equivalent to the engine friction, a problem arises in that, if the cylinder deactivation does not function due to a failure, then the increasing amount of regeneration energy due to deactivating the cylinders cannot be restored, which affects on the energy management of the hybrid vehicle.